Interception and Synthetic Application of Diradical and Diene Forms of Dual‐Nature Azabicyclic o‐Quinodimethanes Generated by 6p‐Azaelectrocyclization

Abstract We demonstrate that 2‐alkenylarylaldimines and ketimines undergo thermal 6π‐azaelectrocyclization to generate a wide range of azabicyclic o ‐quinodimethanes ( o ‐QDMs). These o ‐QDMs exist as a hybrid of a diene and a benzylic diradical. The diradical nature was confirmed by their ability to undergo dimerization and react with H‐atom donor, 2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) and O 2 . In addition, the interception of the diradicaloid o ‐QDMs by H‐atom transfer was used to synthesize five tetrahydroisoquinoline alkaloids and related bioactive molecules. The diene form can undergo 4+2 cycloaddition reactions with different dienophiles to generate bridged azabicycles in high endo:exo selectivity. The azabicyclic o ‐QDMs can be generated for 4+2 cycloaddition from a wide range of electronically and sterically varied 2‐alkenylarylimines, including mono, di, tri and tetrasubstituted alkenes, and imines derived from arylamine, alkylamine (1°, 2°, 3°), benzylamine, benzylsulfonamide and Boc ‐amine.